Oct 29, 2016

When the SETI community adopted protocols for telling the world that ET exists, people mostly got their news from radio, TV and newspapers.

The year was 1989. The internet was a nascent U.S. military-backed project known as ARPANET – the Advanced Research Projects Agency Network. Facebook founder Mark Zuckerberg was 5.

"There was no mention of the internet or social media because they didn't exist," said Arizona attorney Leslie Tennen, a member of the International Academy of Astronautics' SETI Permanent Committee.

The protocols stipulate that the discoverer of a signal from an extraterrestrial civilization notify each of the parties to the "Declaration of Principles Concerning Activities Following the Detection of Extraterrestrial Intelligence" before going public with the news.

"This is designed so that a candidate signal can be tested and confirmed," Tennen said at the International Astronautical Congress in Mexico last month.

The privilege of making the announcement, according to the protocols, is reserved for the discoverer. But in the age of Twitter, Tennen is not sure that confidentiality would be maintained.

"It's difficult to imagine a discovery that would have a greater impact and consequence on society than the announcement of a confirmed detection of intelligent extraterrestrial beings," Tennen said. "The person making the announcement would be an instant international celebrity, never again to have a moment's peace."

The allure of fame may bring pressure on someone to announce the discovery before it is confirmed. Plus, today there are many more researchers involved in the Search for Extraterrestrial Intelligence, or SETI, most of whom have not agreed to follow the voluntary protocols.

The discoverer might, in fact, be someone's personal computer analyzing data for SETI@Home, a distributed computing project backed by the University of California, Berkeley.

"The risk of unauthorized disclosure increases with the number of people having access to the information," Tennen said.

With the rise of social media, Tennen said it is time to revamp the SETI post-detection protocol.

One idea is to designate a single point of information for public release. "We foresee it more as a clearinghouse fir information, not as a censor of the information," Tennen said.

"Of course, this presumes that the information is not going to be embargoed by the government. If that happens then we've got a whole different situation and this discussion takes a completely different track," he added.

The original protocol was developed by the International Academy of Astronautics, with support from the International Institute of Space Law. It was presented to the United Nations' Committee on the Peaceful Uses of Outer Space, which adopted the doctrine as part of its official record, and endorsed by six major international space societies, said Paul Shuch, author of "Searching for Extraterrestrial Intelligence: SETI Past, Present and Future."

The doctrine was revised in 2010, still with no mention of the internet or social media.

Astronomer Dan Werthimer, co-founder and chief scientist for the SETI@Home project, said he believes the protocol should avoid stipulating a particular technology be used to publicize detection of a candidate signal.

"These applications and technologies change so quickly," Werthimer wrote in an email.

The original rock where Jesus Christ is traditionally believed to have been buried in Jerusalem has been exposed to the light of day for the first time in centuries.

According to an exclusive report by National Geographic, a partner in the project at the Church of the Holy Sepulchre, the original rock surface has been covered with marble slabs since at least 1555, and possibly longer. During a conservation project to shore up the shrine surrounding the tomb, a team from the National Technical University of Athens in Greece realized that they would need to access the substructure of the shrine to restore it, said Fredrik Hiebert, the archaeologist-in-residence at the National Geographic Society.

"The Greek conservation group are the first, as far as we know, to actually open this," Hiebert told Live Science. "It's pretty exceptional."

Holy site

Some theological historians believe that Jesus was a real man who was born sometime around the year 1 or earlier in Bethlehem in modern-day Palestine, only later to move to Nazareth in Israel. He is thought to have died around the year 29.

The site venerated as the tomb of Jesus is encased in structures like a Russian nesting doll. According to the Hebrew Bible, Jesus was laid to rest on a stone platform in a cave hewn out of a rock wall. In 326, the first Christian emperor of Rome, Constantine, sent his mother, Helena, as a representative to Jerusalem, where locals pointed out one cave among an area of first-century burials that was said to hold the tomb of Jesus.

Constantine had a shrine installed over the cave. The original top of the cave was removed so that pilgrims could look down and view the slab where Jesus' body was said to have rested. This shrine is known as the Holy Edicule, and it was last reconstructed after a fire in the early 1800s, according to National Geographic. [See Images of Jesus' House and Nazareth Artifacts]

The Holy Edicule itself sits within the Church of the Holy Sepulchre or Church of the Resurrection, which is a famed pilgrimage site and working monastery. It's built directly over the cave where Jesus was said to be buried; another wing sits over the site where he is said to have been crucified. Three sects jointly manage the site: the Greek Orthodox Church, the Roman Catholic Church and the Armenian Orthodox Church. The three groups agreed in 1958 that conservation of the Edicule was necessary, but it's taken nearly 50 years to agree on a method and to secure funding. (According to National Geographic, the project will cost more than $4 million.)

Workers
remove a marble slab covering the original stone "burial bed" where
Jesus Christ is said to have been laid to rest after being crucified. A
layer of loose fill material is seen beneath.

"There was a moment in which you could see on the faces of the important people of the church, a certain happiness that this has actually happened," Hiebert said of the conservation.

Shoring up history

A grid of iron bars installed in the 1940s held the Edicule structure upright until the project started. Now, Hiebert said, the Greek team — with years of experience under their belts of shoring up ancient structures like the Parthenon — will inject mortar around the marble slabs that make up the Edicule.

The conservation team was surprised at how much of the original cave structure remains, he said. They've peeled back marble slabs from the 19th century that were in turn covering slabs from the 15th century, covering slabs from the 12th century, which themselves shield the original bedrock.

As to whether the tomb ever contained the remains of the historical Jesus, "it's a matter of faith," Hiebert said. There are no remains to analyze or DNA evidence to exhume. There is scholarly debate over whether Jesus even existed, said Robert Cargill, an archaeologist and author of "The Cities that Built the Bible" (HarperOne, 2016). A minority of historians think Jesus was a literary construct, said Cargill, who was not involved in the new tomb project, while others think a real person named Jesus existed but that little is known about him.

"We know that Romans crucified people and that people were buried there" in the first and second centuries, Cargill told Live Science. It's also known that there was an oral tradition about the site of Jesus' burial 300 years later, when Helena came to visit Jerusalem.

"We still don't have any [archaeological] evidence that Jesus was crucified, nor do we have evidence that he was crucified there beneath the Church of the Holy Sepulchre," Cargill said.

Oct 27, 2016

A pebble-sized object found in 2004 by a U.K. fossil hunter has just been confirmed as the first known fossilized brain tissue from a dinosaur.

The remarkable discovery, dating to the Cretaceous Period 133 million years ago, offers insight into dinosaur evolution, behavior, intelligence and brain structure.

Scanning electron microscope analysis of the fossil reveals it is a fossilized portion of a brain that belonged to an Iguanodon-like dinosaur. Iguanodon, meaning "Iguana Tooth," was a large, plant-eating dinosaur that lived during the Early Cretaceous. It could grow up to 43 feet long and possibly more, according to some estimates.

David Norman, a University of Cambridge paleontologist, described the fossil's surface as showing "areas of encrusted material that has, under microscopic examination, a curious and highly unusual texture, rather like wrinkled fabric to the naked eye."

Norman said that "wrinkled fabric" is made up of several layers that appear very similar to the meninges — tissue that surround the brain in the brain cavity. The layers of the meninges protect and support the brain's softer tissues.

Animation of the fossilized dinosaur brain tissue (Credit: University of Manchester):

Norman and his team believe that the fossil contains some of the meninges that surrounded the dinosaur's brain, as well as strands of collagen and blood vessels. Structures that could represent tissues from the brain cortex — its outer layer of neural tissue — interwoven with delicate capillaries, also appear to be present.

The brain segment has similarities with the brains of modern-day descendants of dinosaurs, namely birds and crocodiles, strengthening the case that all of these animals are related.

The fossil suggests that the brain was "not a tight fit" in the animal's braincase, Norman said, explaining that, unlike birds, the dinosaur's brain only took up about 50 percent of its braincase's volume.

At first some of the researchers suspected the dinosaur's brain was quite large, since it looks as though the upper brain membranes were pressed against the braincase wall at the top of the animal's skull.

"But, in fact, the only way this specimen could have been preserved was if the head was upside down and the brain has 'flopped' down onto the braincase roof as it started to decay," Norman said.

Co-author Alex Liu of Cambridge's Department of Earth Sciences added, "The chances of preserving brain tissue are incredibly small, so the discovery of this specimen is astonishing."

Iguanodon
(left) with the discovered brain fossil and its parts highlighted.
"Bc," for example, stands for braincase, while "Gm" refers to gray
matter.

The team believes the piece of brain was essentially pickled in a highly acidic and low oxygen body of water shortly after the dinosaur's death. The enormous animal might have keeled over near a bog or swamp. Its cause of death is unknown, but Liu said that "the soft tissues of the brain were likely preserved and cast before the rest of its body was buried in the sediment."

While it's fortunate that where the dinosaur fell allowed part of its brain to be pickled for posterity, Norman points out that the "acidic 'pickling' process would have denatured any of the biological molecules." That means no DNA can now be extracted from the fossil.

Nevertheless, "Any time we get soft tissue preservation in a dinosaur it's cause for celebration since it gives us such a unique window into the biology of these animals," Lawrence Witmer, a professor of anatomy and paleontology at Ohio University who did not work on the research, told Seeker.

A labeling error and reckless media hype in the 1980s led to unjustly branding a gay airline employee as "Patient Zero" in the US AIDS epidemic, scientific and historical sleuthing detailed Wednesday.

The deadly virus, which has claimed more than 650,000 lives in the United States in over four decades, jumped from the Caribbean to New York City around 1970, researchers reported in the journal Nature.

A 33-year old blood sample analyzed with new techniques proves once-and-for-all that the man posthumously vilified as the American HIV epicenter, Gaetan Dugas, was simply one of the disease's many victims.

Before he died in 1984, he helped scientists trace how AIDS had spread by identifying dozens of his sexual partners.

"Dugas is one of the most demonized patients in history," said Richard McKay, a public health historian and one of the study's two lead authors.

The story of "Patient Zero" began in 1982 when investigators from the US Centers for Disease Control (CDC) realized that several men in Southern California suffering from a rare, lethal lung infection were linked by sexual relations.

As the scientists conducted patient interviews to reconstruct their social network and trace the infection -- not yet known as acquired immune deficiency syndrome, or AIDS -- back to it source, one man in particular came up repeatedly: Gaetan Dugas.

In keeping with protocol, they assigned him a number, 057.

But because he was from New York and not Los Angeles, where the investigation was unfolding, they added an "O" for "Outside-of-California" in their notes.

But soon researchers "began interpreting the ambiguous oval as a digit, and referring to 'Patient O' as 'Patient 0' (zero)," said McKay.

At the same time, health officials began to realize just how extensive the potential network of infection might be.

Over 65 percent of the gay men in the Los Angeles disease cluster reported more than 1,000 sexual partners in their lifetimes, and over 75 percent had had 50 in the previous year alone.

Case 057 -- Dugas -- managed to name 72 of the roughly 750 men he had been with in the previous three years, far more than most of the others interviewed.

This very fact, combined with his unusual and memorable name, may have contributed to his later notoriety, McKay speculated.

When the scientific study based on the investigation was published in 1984, "Patient 0" stood out in a diagram which suggested he was the viral lynchpin between the east and west coast outbreaks of the disease.

Two years later, an enterprising journalist discovered Dugas' name and cast him as a super-villain in his influential book on the AIDS crisis, "And the Band Played On."

It has long been clear to experts that the US HIV epidemic did not start with this hapless French-Canadian living in the Big Apple, but biological evidence has been lacking.

Until now.

To lay the case to rest, co-lead author Michael Worobey from the University of Arizona developed a new technique for recovering genetic material from the HIV virus in decades-old blood samples.

The method, called RNA jackhammering, breaks down the huge human genome in the degraded blood sample into tiny overlapping chunks.

This, in turn, makes it possible to extract genetic material, called RNA, from the virus.

By extracting viral DNA from more than 2,000 blood samples collected from US men in 1978 and 1979, the scientists showed that HIV already displayed a high level of genetic diversity in the 1970s.

Spectacular photos captured by NASA's Cassini spacecraft reveal a curious color change over Saturn's north pole. The occurrence may be linked to seasonal changes and the planet's enormous hexagonal jet stream.

The images were captured by Cassini's wide-angle camera between 2012 and 2016. Photos from 2012 show a bluish halo over Saturn's north pole, while those taken in 2016 show the same area with a more golden hue.

Saturn's north pole has a unique, six-sided jet stream known as "the hexagon," which is approximately 20,000 miles (32,000 kilometers) wide. Winds of this hexagonal vortex whip through the planet's atmosphere at approximately 200 mph (322 km/h).

Preliminary hypotheses suggest the color change observed in the atmosphere over Saturn's northern hemisphere could be associated with the jet stream. For instance, the hexagonal vortex may act as barrier and prevent surrounding particles from entering the area. In this case, the sky over Saturn's north pole would have been cleared of haze or aerosols during the seven-year-long Saturnian winter, according to a statement from NASA. Then, haze production would have ramped up again when the pole was exposed to sunlight.

"Scientists are investigating potential causes for the change in color of the region inside the north-polar hexagon on Saturn," NASA officials said in the statement. "The color change is thought to be an effect of Saturn's seasons. In particular, the change from a bluish color to a more golden hue may be due to the increased production of photochemical hazes in the atmosphere as the north pole approaches summer solstice in May 2017."

The observed color change in Saturn's north polar region between 2012 and 2016.

Photochemical hazes, or aerosols, are created from reactions between sunlight and the atmosphere. Saturn experienced equinox in August 2009, and since then has been subjected to continuous sunshine. During this time, photochemical aerosols have accumulated in the sky above Saturn's north pole, creating the golden haze observed today.

We observe the universe in many different wavelengths of the electromagnetic spectrum (and now, the gravitational wave spectrum) to see different objects radiating at different energies. Seeing the universe in infrared light, for example, can help us see baby stars forming inside their dusty stellar nurseries, whereas X-ray observatories can pick out some of the most energetic phenomena like the flares produced by black holes consuming stars.

However, as these wavelengths are often beyond the visible spectrum (i.e. light that the human eye can see), astronomers will assign familiar colors to these otherwise invisible wavelengths to give them meaning.

And so, in a stunning portrait created by data from the Murchison Widefield Array (MWA) located in the West Australian outback, a beautiful technicolor display has been produced of our radio wave view of the cosmos.

"The human eye sees by comparing brightness in three different primary colors — red, green and blue," said Natasha Hurley-Walker, of Curtin University and the International Center for Radio Astronomy Research (ICRAR), in a Royal Astronomy Society statement. "GLEAM does rather better than that, viewing the sky in each of 20 primary colors. That's much better than we humans can manage, and it even beats the very best in the animal kingdom, the mantis shrimp, which can see 12 different primary colors."

The GaLactic and Extragalactic All-sky MWA — or 'GLEAM' survey — has cataloged 300,000 galaxies observed at frequencies between 70 and 230 MHz and, after assigning a color to the frequency range, a striking picture emerges.

Through the center of the image is the band of the Milky Way, our home galaxy. Beyond our galaxy's emissions are low frequency radio waves (shown in red) to the mid-range frequencies (green) to high frequency radio waves (blue). Some of these radio emissions have traveled for billions of light-years since the early epochs of our universe, whereas the emissions from our galaxy were produced on our cosmic doorstep, but all have a story to tell astronomers.

"Our team are using this survey to find out what happens when clusters of galaxies collide," said Hurley-Walker. "We're also able to see the remnants of explosions from the most ancient stars in our galaxy, and find the first and last gasps of supermassive black holes."

Israeli authorities displayed on Wednesday a rare papyrus fragment, older than the Dead Sea Scrolls, which features the earliest known Hebrew reference to Jerusalem outside the Bible.

The Israel Antiquities Authority (IAA) recovered the fragile document after it was plundered from a cave in the Judean Desert cave by a band of antiquity robbers.

Radiocarbon dating has determined it dates back to the 7th century BC. This is the time of the First Temple, which, according to the Hebrew Bible, was constructed by King Solomon in 957 B.C. and then destroyed 400 years later by the Babylonian king Nebuchadnezzar, who exiled many Jews.

Two lines of ancient Hebrew script are clearly visible on the 4-by-1 inch fragment.

"From the king's maidservant, from Naʽarat [a place near Jericho], jars of wine, to Jerusalem," the 2,700 year papyrus reads.

According to experts at the IAA, the fragment was part of a shipping document which detailed the payment of taxes or transfer of goods to storehouses in Jerusalem, the capital city of the kingdom of Judea at that time.

"It's the first time we encounter the name Jerusalem on a papyrus, which was probably written by a woman. That's very exciting, said Pnina Shor, curator and director of the Dead Sea Scroll Project at IAA.

She noted the woman had an unusually high status in the administration of the Kingdom of Judah.

The ancient document is now wrapped in bitter controversy and politics. Israeli authorities showed it as evidence of the Jewish connection to the holy city on the same day UNESCO, the UN's world heritage organization, approved a resolution that, according to Israel, ignores Jewish ties to Temple Mount, Judaism's holiest site.

Sacred to the three great monotheistic religions — Judaism, Christianity, and Islam –— Temple Mount is one of the most disputed plots of land on Earth.

A revered site to Christians, Temple Mount is venerated by Jews as the location where Solomon's temple once stood and later Herod's temple. It abuts the Western Wall — the only remainder of the Roman sacking of the Second Temple in 70 A.D.

But it's also the third-holiest site in Islam. Known to Arabs as Haram Sharif, it includes the Al Aqsa mosque and the Dome of the Rock, a massive golden dome that houses the rock where the Prophet Mohammed is said to have ascended to heaven.

UNESCO's document refers to the disputed plot of land only as a "Muslim holy site of worship."

According to MK Miri Regev, Israel's Minister of Culture and Sport, the recovered papyrus proves beyond doubt the historic connection between Jews and Jerusalem.

Oct 26, 2016

Although the universe started out with a bang it quickly evolved to a relatively cool, dark place. After a few hundred thousand years the lights came back on and scientists are still trying to figure out why.

Astronomers know that reionization made the universe transparent by allowing light from distant galaxies to travel almost freely through the cosmos to reach us.

However, astronomers don't fully understand the escape rate of ionizing photons from early galaxies. That escape rate is a crucial, but still a poorly constrained value, meaning there are a wide range of upper and lower limits in the models developed by astronomers.

That limitation is in part due to the fact that astronomers have been limited to indirect methods of observation of ionizing photons, meaning they may only see a few pixels of the object and then make assumptions about unseen aspects. Direct detection, or directly observing an object such as a galaxy with a telescope, would provide a much better estimate of their escape rate.

In a just-published paper, a team of researchers, led by a University of California, Riverside graduate student, used a direct detection method and found the previously used constraints have been overestimated by five times.

"This finding opens questions on whether galaxies alone are responsible for the reionization of the universe or if faint dwarf galaxies beyond our current detection limits have higher escape fractions to explain radiation budget necessary for the reionization of the universe," said Kaveh Vasei, the graduate student who is the lead author of the study.

It is difficult to understand the properties of the early universe in large part because this was more than 12 billion year ago. It is known that around 380,000 years after the Big Bang, electrons and protons bound together to form hydrogen atoms for the first time. They make up more than 90 percent of the atoms in the universe, and can very efficiently absorb high energy photons and become ionized.

However, there were very few sources to ionize these atoms in the early universe. One billion years after the Big Bang, the material between the galaxies was reionized and became more transparent. The main energy source of the reionization is widely believed to be massive stars formed within early galaxies. These stars had a short lifespan and were usually born in the midst of dense gas clouds, which made it very hard for ionizing photons to escape their host galaxies.

Previous studies suggested that about 20 percent of these ionizing photons need to escape the dense gas environment of their host galaxies to significantly contribute to the reionization of the material between galaxies.

Unfortunately, a direct detection of these ionizing photons is very challenging and previous efforts have not been very successful. Therefore, the mechanisms leading to their escape are poorly understood.

This has led many astrophysicists to use indirect methods to estimate the fraction of ionizing photons that escape the galaxies. In one popular method, the gas is assumed to have a "picket fence" distribution, where the space within galaxies is assumed to be composed of either regions of very little gas, which are transparent to ionizing light, or regions of dense gas, which are opaque. Researchers can determine the fraction of each of these regions by studying the light (spectra) emerging from the galaxies.

In this new UC Riverside-led study, astronomers directly measured the fraction of ionizing photons escaping from the Cosmic Horseshoe, a distant galaxy that is gravitationally lensed. Gravitational lensing is the deformation and amplification of a background object by the curving of space and time due to the mass of a foreground galaxy. The details of the galaxy in the background are therefore magnified, allowing researchers to study its light and physical properties more clearly.

Based on the picket fence model, an escape fraction of 40 percent for ionizing photons from the Horseshoe was expected. Therefore, the Horseshoe represented an ideal opportunity to get for the first time a clear, resolved image of leaking ionizing photons to help understand the mechanisms by which they escape their host galaxies.

The research team obtained a deep image of the Horseshoe with the Hubble Space Telescope in an ultraviolet filter, enabling them to directly detect escaping ionizing photons. Surprisingly, the image did not detect ionizing photons coming from the Horseshoe. This team constrained the fraction of escaping photons to be less than 8 percent, five times smaller than what had been inferred by indirect methods widely used by astronomers.

"The study concludes that the previously determined fraction of escaping ionizing radiation of galaxies, as estimated by the most popular indirect method, is likely overestimated in many galaxies," said Brian Siana, co-author of the research paper and an assistant professor at UC Riverside. "The team is now focusing on direct determination the fraction of escaping ionizing photons that do not rely on indirect estimates."

Buddhist prayer flags in the Himalaya mountains, Nepal. The Himalayas
have produced some of the world's largest earthquakes, like the April
2015 Gorkha earthquake.

The main fault at the foot of the Himalayan mountains can likely generate destructive, major earthquakes along its entire 2,400-kilometer (1,500-mile) length, a new study finds. Combining historical documents with new geologic data, the study shows the previously unstudied portion of the fault in the country Bhutan is capable of producing a large earthquake and did so in 1714.

"We are able for the first time to say, yes, Bhutan is really seismogenic, and not a quiet place in the Himalayas," said György Hetényi, a geophysicist at the University of Lausanne, Switzerland and lead author of the new study accepted for publication in Geophysical Research Letters, a journal of the American Geophysical Union.

The Himalayas have produced some of the world's largest earthquakes, like the April 2015 Gorkha earthquake that devastated Nepal. But scientists had not been able to prove whether every region along the 2,400-kilometer arc was seismogenic, or capable of producing quakes. Bhutan was one of the last open gaps along the mountain chain: the country had no records of recent major earthquakes and no major seismological work had been done there.

Confining a major earthquake to Bhutan in 1714, like the new study does, means the entire Himalayan arc has experienced a major earthquake in the past 500 years, according to the study's authors. By filling this gap, the new study helps the millions of residents in the region understand its potential for natural hazards, according to Hetényi.

"We provide a longer and therefore more representative record of seismicity in Bhutan, and this makes better hazard estimates," he said.A nation apart

The highest mountain range on Earth, the Himalayas are the product of the Indian tectonic plate subducting under the Eurasian Plate. The mountains span a northwest to southeast arc roughly 2,400 kilometers (1,500 miles) long, nearly the distance between the U.S. East and West coasts.

Throughout the 20th century, Bhutan, a small nation east of Nepal sandwiched between India and China, had been relatively isolated from the outside world and scientists were rarely allowed inside its borders. Until recently, researchers thought Bhutan could be the only major segment of the Himalayas not to have experienced a major earthquake in the last 500 years, according to Hetényi.

But, after a magnitude 6 earthquake struck the country in 2009, the government opened the door for scientists to perform geophysical research, Hetényi said.

Hetényi and his colleagues made several trips to the country from 2010 to 2015 to catalog small earthquakes in the area and study how the structure of the Indian Plate changes as it subducts below the crushing belt of mountains. One question they were hoping to answer was whether Bhutan had historically experienced any major destructive earthquakes.

Historical records of earthquakes in Bhutan are rare, but by luck Hetényi stumbled upon a biography of famous 18th century Buddhist monk and temple builder Tenzin Lekpai Dondup. The biography described a quake in early May of 1714 that destroyed the Gangteng monastery Dondup helped build.

The biography and other historical records indicated there were many aftershocks, meaning it could have been a major quake, according to Hetényi.

However, this description alone did not pinpoint where the quake occurred.

"When you only have very local devastation descriptions, you never know whether this devastation is due to an intermediate earthquake that occurred locally, nearby the chronicler, or whether it's the result of a bigger earthquake that occurred over greater distances," said Laurent Bollinger, a geologist at the French Alternative Energies and Atomic Energy Commission who was not involved in the new study.

While in Bhutan, several of Hetényi's colleagues dug trenches around the fault line to see if one side of it had moved vertically with respect to the other side -- which would be considered evidence of a major earthquake. That study, led by Romain Le Roux-Mallouf, a geologist at the University of Montpellier, France, found evidence of rock uplift on one side of the fault had taken place between 1642 and 1836. Hetényi combined the results from that study with historical records of the 1714 earthquake to pinpoint where the 1714 quake happened and how large it was.

Hetényi's analysis revealed the 1714 quake likely caused the rock uplift his colleagues observed around the fault. The earthquake likely occurred in west central Bhutan, where most of the population lives, and had a magnitude of at least 7.5 to 8.5, Hetényi said. By comparison, the April 2015 Gorkha earthquake had a magnitude of 7.8.

The star KIC 8462852 — informally known as Tabby's Star — has been the focus of the worlds' attention for months now, and for good reason. Its strange behavior could be a sign that there's a super-advanced alien civilization carrying out the mother of all engineering projects in orbit. But the mysterious dips in observed light from the star could alternatively just be a huge swarm of comets or some other as-yet-to-be-understood stellar phenomenon.

Although astronomers are generally skeptical that there really is an extraterrestrial civilization constructing a starlight-blocking megastructure only 1,480 light-years from Earth, the Breakthrough Listen SETI (Search for Extraterrestrial Intelligence) project is committing radio telescope time of one of the most powerful observatories on the planet to at least test the intelligent alien hypothesis.

The project is a part of the $100 million Breakthrough Prize Foundation that's funded by Russian entrepreneur Yuri Milner and backed by British theoretical physicist Stephen Hawking and Facebook founder Mark Zuckerberg.

Starting Wednesday (Oct. 26), a team of astronomers will use the renowned 100-meter Green Bank Telescope (pictured above) that is located deep in a radio-silent corner of West Virginia to study Tabby's Star. For eight hours per night for three nights over the next two months, a special instrument attached to the huge radio telescope will be used to carry out an unprecedented observation campaign of the star.

"The Breakthrough Listen program has the most powerful SETI equipment on the planet, and access to the largest telescopes on the planet," said Andrew Siemion, director of the Berkeley SETI Research Center and co-director of Breakthrough Listen, in a statement. "We can look at it with greater sensitivity and for a wider range of signal types than any other experiment in the world."

Although other projects have tried to eavesdrop on the star before, SETI campaigns have typically been limited by the number of radio frequencies that can be recorded simultaneously and the amount of time committed to just one star in the sky. This new instrument is able to record a huge amount of data across a range of frequencies at the same time, potentially allowing us to detect the radio transmissions from any transmitting intelligent aliens at Tabby's Star.

"The Green Bank Telescope is the largest fully steerable radio telescope on the planet, and it's the largest, most sensitive telescope that's capable of looking at Tabby's star given its position in the sky," said Siemion. "We've deployed a fantastic new SETI instrument that connects to that telescope, that can look at many gigahertz of bandwidth simultaneously and many, many billions of different radio channels all at the same time so we can explore the radio spectrum very, very quickly."

It's estimated that up to one petabyte of data may be collected over the observing run — that's enough data to fill a thousand computer hard drives (assuming each can store one terabyte). The researchers say that it could be over a month before we know whether or not a signal was detected because it will take a long time to process all the observations.

With Siemion, Tabetha Boyajian, from Louisiana State University, and visiting UC Berkeley astronomer Jason Wright will be heading the study. Boyajian was the first to report on KIC 8462852's peculiar light-curve in September 2015, which was initially flagged by citizen scientists participating in the Planet Hunters project. Tabby's Star is so-named in honor of Boyajian.

The project asks for the help of the public to look at candidate exoplanet transits from NASA's Kepler Space Telescope. Kepler has confirmed hundreds of worlds orbiting other stars by detecting the dip in brightness of a star (described by the star's "light-curve") by an exoplanet passing in front — an event known as a "transit." And the transit signal produced by Tabby's star was as dramatic as it was bizarre.

Typically, an exoplanet signal might dim a star's light by around 2%. But several of the irregular transits of Tabby's Star caused the starlight to drop by up to 22%. This means that something very big must be passing in front. What's more, it seems the star's brightness has been dimming for hundreds of years according to historical astronomical records, only adding to the intrigue. Although several ideas have been put forward to explain the signal, the key one being the possibility of a huge cloud of comets drifting in front of the star, all have fallen short of fully explaining the Kepler observation.

Evidence is mounting that humans played a primary role in the extinction of European cave lions, with new research finding that cavemen hunted the big cats for their pelts not too long before the lions disappeared from the face of the Earth.

One pelt once even decorated part of the cave site floor of La Garma in northern Spain, probably for symbolic and ritualistic purposes. Its remains, dating to about 16,000 years ago, are described in PLOS ONE.

The skin of animals was most commonly used to make clothing, "but this was not a common pelt," Marián Cueto of the University of Cantabria, Spain, told Seeker. "It comes from a lion, a very dangerous animal and surely one that was really difficult to hunt, so it probably had an important role as a trophy."

She went on to say that many societies, both past and present, viewed lions as symbols of power.

All that's left of the pelt are the lion's claws, which retain marks consistent with human modification of the overall pelt.

"We have observed cut-marks made by a silex (ground stone) instrument in all of them, indicating they separated the claws from the rest of the foot," Cueto explained. "These cut-marks are very clear and show expertise in skinning lions. They had knowledge of the anatomy: where to cut in the exact place."

Early Europeans could not have ignored cave lions, since female lions inhabited caves to raise their cubs and no doubt encountered people from time to time. Humans also hunted reindeer and other cave lion prey.

Cueto and her team suspect that, as the human population increased in Europe, they pushed out the cave lions in multiple ways, including killing them. Humans also contributed to the extinction of other iconic Ice Age animals. At least 177 large mammals, including the cave lion, went extinct as this era drew to a close. They include woolly mammoths, saber-tooth cats, mastodons and giant sloths.

The European cave lion bit the dust even earlier -- around 14,000 years ago -- so our hunting of them likely sped up the extinction.

No one knows just what these long-gone lions looked like. As Cueto said, "It's not easy describing the fur of an animal extinct in the Pleistocene because we have only recovered its skeleton."

The cave lion's skeleton is bigger but otherwise identical to modern lions, so scientists assume the animals would have looked pretty similar.

She added, however, that cave lions were included in cave paintings. Drawings of lions appear on the walls of caves at Chauvet (France), for example. Prehistoric figurines from Vogelherd Cave (Germany) also exist.

Oct 25, 2016

As with everything in life, too much of a good thing can be bad — and that logic now seems to apply to alien life, too.

Since Proxima Centauri b (or just Proxima b) was discovered in August, countless imaginings as to what the small, Earth-sized planet would look like up-close have captivated the media. Is the planet truly Earth-like with mountains, oceans, lush green continents and an atmosphere in just the right proportions to support extraterrestrial life? Or is it actually a dry, barren hellhole being constantly irradiated by its star? It could go either way.

As Proxima b was only detected by its gravitational influence on Proxima Centauri — the small exoplanet's orbit causes the tiny star to wobble — we only know its mass and orbital period. But these two characteristics are exciting. Not only is Proxima b of approximate Earth-mass, it also orbits within the star's habitable zone, the region surrounding a star that is neither too hot or too cold for liquid water to exist on the surface.

On Earth, where there's liquid water, there's life. So if Proxima b has water on its surface, it might also be in a liquid state, so there's certainly some excitement surrounding the possibility that the world may also play host to life. But so far, we have absolutely zero evidence that water is even there, so its life-giving potential is purely speculative.

Now, in new research by astrophysicists at the University of Bern, they've tackled this problem with planetary evolution models and found that red dwarf stars may preferentially host small, rocky worlds. Not only that, these worlds would likely contain large quantities of water.

"Our models succeed in reproducing planets that are similar in terms of mass and period to the ones observed recently," said Yann Alibert, of the Center of Space and Habitability (CSH) at the University of Bern, in a statement. "Interestingly, we find that planets in close-in orbits around these type of stars are of small sizes. Typically, they range between 0.5 and 1.5 Earth radii with a peak at about 1.0 Earth radius. Future discoveries will tell if we are correct!"

From this study, which has been accepted for publication in the journal Astronomy & Astrophysics, these small alien worlds also evolved with huge quantities of water. For 90% of the exoplanets simulated, their total mass consisted of over 10% water. Considering Earth is only 0.02% water, the simulated red dwarf exoplanets are veritable ocean planets!

At first glance, this might seem like an incredible opportunity for advanced life forms to evolve on planets in red dwarf systems. After all, red dwarfs are among the most ancient of stars in our galaxy and have a predicted lifespan of longer than the age of the universe (14 billion years). Life on Earth only sprung into being 3 billion years ago when our sun was young; life on red dwarf worlds could evolve over epic timescales by comparison.

And now it seems that, according to established planetary formation theories, these ancient worlds could have a plentiful supply of water? Well, the mind boggles.

But a huge supply of water on small exoplanets orbiting red dwarfs may not necessarily be a good thing. "While liquid water is generally thought to be an essential ingredient, too much of a good thing may be bad," said study co-author Willy Benz.

The Caraga region of northeast Mindanao, an island in the southern Philippines, has been identified as the top biodiversity hot spot for amphibians and reptiles in the country, the region boasting more species, for an area of its size, than any other in the Philippines.

That's according to researchers who have just documented 126 species in the area — including an array of frogs, snakes, lizards, turtles and crocodiles — in a new study in the online journal ZooKeys.

The island, with a history of environment loss, thanks largely to illegal logging in the timber-rich location, made for a challenging study subject, in terms of species location and documentation.

"Mindanao is a place where, unfortunately, the original forest cover was more than 85 percent, but now it's down to 6 percent original forest, and 15 percent is second-growth vegetation," said study co-author Rafe Brown, University of Kansas curator-in-charge of herpetology, in a statement.

"Mindanao has extensive mineral resources and forests with valuable timber," Brown explained. "Tropical rainforest soils are also very fertile, making the lowlands attractive to agribusiness. There's been conflict over those resources for hundreds of years."

Nonetheless, Brown and his colleagues forged on. Their efforts to explore the region paid off, to the tune of cataloging 49 lizards, 40 frogs, 35 snakes, a crocodile and a freshwater turtle.

And what efforts. It's one thing to ponder the number of species and another to actually have to go find them.

"We typically dig around tree trunks looking for animals that live underground," Brown said. "We search rivers and streams, turning over rocks, splitting open decaying logs looking for lizards or frogs. We climb trees, looking for tree-dwelling lizards, or place pitfall traps in the ground to catch lizards and small snakes that live in the leaf litter. We also use sticky traps like people use to catch pests in homes."

Here are a few of the critters Brown and his colleagues documented:

A white-lined water snake (Rhabdophis auriculata auriculata):

A frilled tree frog (Kurixalus appendiculatus):

And this cool, two-spotted flying lizard (Draco bimaculatus):

"The biodiversity is so high in this one pocket of northeast Mindanao, largely because the ranges of so many species in the archipelago overlap in this one area," said Brown. "We knew it was really diverse, but we didn't have a sense of this one area being the bull's-eye, the epicenter of this diversity."

So many new subterranean bacteria groups have just been found that the tree of life required a major revision.

The discovery of 47 new bacterial groups has just been reported from a single aquifer in Colorado, providing a vivid reminder of just how much life exists in the still mysterious subterranean world below our feet.

When added to 35 other new bacterial groups that were documented last year, the findings -- published in the journal Nature Communications -- double the number of the planet's known bacterial groups. As a result, dozens of new branches have just been added to the tree of life, essentially requiring a major revision of that all-encompassing diagram.

All of the known major bacterial groups are represented by wedges in this circular 'tree of life.'

"We did not initially expect anything like the diversity that was encountered at the site," co-author Jill Banfield told Seeker, explaining that she and her team started working on the Rifle aquifer along the Colorado River in west central Colorado "over a decade ago with the objective of studying microbes that remove uranium contamination from groundwater."

Banfield is a senior faculty scientist in Berkeley Lab's Climate & Ecosystem Sciences Division and a UC Berkeley professor. As the years went on at the research site near Rifle, Colo., she and her team noticed how complex and interconnected the microbial world there was -- so they developed the research site into a model system to study underground microbiology.

The researchers found so many new microbes that they struggled over how to name them. The prior study mentioning the 35 other groups drew from past Microbiology Award winners. For this latest research, they "decided to honor well-regarded microbiologists from around the world," Banfield said. "We made sure to strike a gender balance to ensure that women were given their due."

To detect such tiny microbes, the scientists sent soil and water samples to the Joint Genome Institute for sequencing. The high-tech method isolates and purifies DNA from environmental samples, and then sequences 1 trillion base pairs of DNA at a time. Banfield's lab developed tools to analyze the data, permitting the reconstruction of the genomes of more than 2,500 microbes.

The underground microbes may be tiny, but they are more important than most of us probably think.

Lead author Karthik Anantharaman told Seeker that they are involved in many essential processes, such as breaking down the components of fertilizers. Nitrate from fertilizers can enter groundwater, where it may lead to the production of one of the most potent greenhouse gases, nitrous oxide, if certain microbes are inactive.

As for how microbes deal with fertilizers and other substances, Anantharaman explained that one microbe's waste is another microbe's food. This creates a tightly interconnected system.

"It is striking," he said, "that microbes need teamwork to complete tasks. It is precisely this lack of effective teamwork that can throw processes off sync and lead to release of greenhouse gases like nitrous oxide."

Io's volcanism is unmatched by any other rocky body in the solar system. As Jupiter's innermost and third-largest moon, it is at the mercy of the gas giant's powerful tides. As a result, it is constantly erupting, unleashing incredibly powerful explosions, spewing molten rock all over its tortured surface.

Now, astronomers have been able to gather observations of the 2,000 mile-wide Io with two of the world's most powerful telescopes, watching it burn over two years.

"On a given night, we may see half a dozen or more different hot spots," said Katherine de Kleer, of UC Berkeley who led the 29 months of near-infrared observations using the 10-meter Keck II and the 8-meter Gemini North telescopes atop Mauna Kea in Hawaii. It is perhaps a little poetic that Mauna Kea is also a volcano, albeit a dormant one. "Of Io's hundreds of active volcanoes, we have been able to track the 50 that were the most powerful over the past few years."

As Io orbits Jupiter, slight changes in the moon's orbital distance can cause pretty dramatic changes in the tidal forces it experiences, causing friction from tidal heating. This mechanism delivers a huge amount of energy to Io's interior, keeping it in a molten state and driving perpetual volcanism.

During
a flyby of Io in 1999, NASA's Jupiter mission Galileo captured this
true-color observation of volcanic Io. Note the lack of impact craters;
the surface of Io is constantly being renewed by fresh layers of lava.

By observing Io for so long, de Kleer's team was able to test some of the theoretical models that are thought to best describe the moon's eruptions. According to theory, the majority of the eruptions should be located either near the poles or the equator and, as Io is tidally locked to Jupiter, the pattern of volcanoes should be symmetrical between the forward-facing and rear-facing (to the direction of its orbit) hemispheres.

But on analyzing 100 days-worth of observations between August 2013 and December 2015, they found a surprising number of powerful, but short-lived eruptions all occurred on the rear-facing hemisphere and at higher latitudes than longer-lived eruptions.

"The distribution of the eruptions is a poor match to the model predictions," de Kleer said in a statement, "but future observations will tell us whether this is just because the sample size is too small, or because the models are too simplified. Or perhaps we'll learn that local geological factors play a much greater role in determining where and when the volcanoes erupt than the physics of tidal heating do."

Io, as seen in near-infrared wavelengths, exhibits a huge number of volcanic eruptions.

Another interesting finding focused on Loki Patera, Io's longest-living volcano that is believed to be a vast lake of molten lava. Every 2 years or so, it is believed the lava lake's cooling crust overturns, much like lava lakes that are found on Earth, triggering an intense brightening, and sending a wave of heat emissions around the lake. This causes destabilization and sinking of more crust and further heating.

Oct 24, 2016

Computer simulations by astrophysicists at the University of Bern of the formation of planets orbiting in the habitable zone of low mass stars such as Proxima Centauri show that these planets are most likely to be roughly the size of Earth and to contain large amounts of water.

In August 2016, the announcement of the discovery of a terrestrial exoplanet orbiting in the habitable zone of Proxima Centauri stimulated the imagination of the experts and the general public. After all this star is the nearest star to our sun even though it is ten times less massive and 500 times less luminous. This discovery together with the one in May 2016 of a similar planet orbiting an even lower mass star (Trappist-1) convinced astronomers that such red dwarfs (as these low mass stars are called) might be hosts to a large population of Earth-like planets.

How could these objects look like? What could they be made of? Yann Alibert and Willy Benz at the Swiss NCCR PlanetS and the Center of Space and Habitability (CSH) at the University of Bern carried out the first computer simulations of the formation of the population of planets expected to orbit stars ten times less massive than the sun.

"Our models succeed in reproducing planets that are similar in terms of mass and period to the ones observed recently," Yann Alibert explains the result of the study that has been accepted for publication as a Letter in the journal "Astronomy and Astrophysics." "Interestingly, we find that planets in close-in orbits around these type of stars are of small sizes. Typically, they range between 0.5 and 1.5 Earth radii with a peak at about 1.0 Earth radius. Future discoveries will tell if we are correct!" the researcher adds.

Ice at the bottom of the global ocean

In addition, the astrophysicists determined the water content of the planets orbiting their small host star in the habitable zone. They found that considering all the cases, around 90% of the planets are harbouring more than 10% of water. For comparison: Earth has a fraction of water of only about 0,02%. So most of these alien planets are literally water worlds in comparison! The situation could be even more extreme if the protoplanetary disks in which these planets form live longer than assumed in the models. In any case, these planets would be covered by very deep oceans at the bottom of which, owing to the huge pressure, water would be in form of ice.

Water is required for life as we know it. So could these planets be habitable indeed? "While liquid water is generally thought to be an essential ingredient, too much of a good thing may be bad," says Willy Benz. In previous studies the scientists in Bern showed that too much water may prevent the regulation of the surface temperature and destabilizes the climate. "But this is the case for Earth, here we deal with considerably more exotic planets which might be subjected to a much harsher radiation environment, and/or be in synchronous " he adds.Following the growth of planetary embryos

To start their calculations, the scientists considered a series of a few hundreds to thousands of identical, low mass stars and around each of them a protoplanetary disk of dust and gas. Planets are formed by accretion of this material. Alibert and Benz assumed that at the beginning, in each disk there were 10 planetary embryos with an initial mass equal to the mass of the Moon. In a few day's computer time for each system the model calculated how these randomly located embryos grew and migrated. What kind of planets are formed depends on the structure and evolution of the protoplanetary disks.

The universe may not be expanding at an accelerating rate, as previously
thought, but rather, at a constant rate, suggests new research.

Five years ago, the Nobel Prize in Physics was awarded to three astronomers for their discovery, in the late 1990s, that the universe is expanding at an accelerating pace.

Their conclusions were based on analysis of Type Ia supernovae -- the spectacular thermonuclear explosion of dying stars -- picked up by the Hubble space telescope and large ground-based telescopes. It led to the widespread acceptance of the idea that the universe is dominated by a mysterious substance named 'dark energy' that drives this accelerating expansion.

Now, a team of scientists led by Professor Subir Sarkar of Oxford University's Department of Physics has cast doubt on this standard cosmological concept. Making use of a vastly increased data set -- a catalogue of 740 Type Ia supernovae, more than ten times the original sample size -- the researchers have found that the evidence for acceleration may be flimsier than previously thought, with the data being consistent with a constant rate of expansion.

The study is published in the Nature journal Scientific Reports.

Professor Sarkar, who also holds a position at the Niels Bohr Institute in Copenhagen, said: 'The discovery of the accelerating expansion of the universe won the Nobel Prize, the Gruber Cosmology Prize, and the Breakthrough Prize in Fundamental Physics. It led to the widespread acceptance of the idea that the universe is dominated by "dark energy" that behaves like a cosmological constant -- this is now the "standard model" of cosmology.

'However, there now exists a much bigger database of supernovae on which to perform rigorous and detailed statistical analyses. We analysed the latest catalogue of 740 Type Ia supernovae -- over ten times bigger than the original samples on which the discovery claim was based -- and found that the evidence for accelerated expansion is, at most, what physicists call "3 sigma." This is far short of the "5 sigma" standard required to claim a discovery of fundamental significance.

'An analogous example in this context would be the recent suggestion for a new particle weighing 750 GeV based on data from the Large Hadron Collider at CERN. It initially had even higher significance -- 3.9 and 3.4 sigma in December last year -- and stimulated over 500 theoretical papers. However, it was announced in August that new data shows that the significance has dropped to less than 1 sigma. It was just a statistical fluctuation, and there is no such particle.'

There is other data available that appears to support the idea of an accelerating universe, such as information on the cosmic microwave background -- the faint afterglow of the Big Bang -- from the Planck satellite. However, Professor Sarkar said: 'All of these tests are indirect, carried out in the framework of an assumed model, and the cosmic microwave background is not directly affected by dark energy. Actually, there is indeed a subtle effect, the late-integrated Sachs-Wolfe effect, but this has not been convincingly detected.

'So it is quite possible that we are being misled and that the apparent manifestation of dark energy is a consequence of analysing the data in an oversimplified theoretical model -- one that was in fact constructed in the 1930s, long before there was any real data. A more sophisticated theoretical framework accounting for the observation that the universe is not exactly homogeneous and that its matter content may not behave as an ideal gas -- two key assumptions of standard cosmology -- may well be able to account for all observations without requiring dark energy. Indeed, vacuum energy is something of which we have absolutely no understanding in fundamental theory.'

This image depicts mouse embryos with the ZRS from cobra or python
inserted into their genomes, replacing the normal gene regulator. Their
truncated limb development is visible in the comparative bone scans.

Snakes lost their limbs over 100 million years ago, but scientists have struggled to identify the genetic changes involved. A Cell paper publishing October 20 sheds some light on the process, describing a stretch of DNA involved in limb formation that is mutated in snakes. When researchers inserted the snake DNA into mice, the animals developed truncated limbs, suggesting that a critical stretch of DNA lost its ability to support limb growth during snake evolution.

"This is one of many components of the DNA instructions needed for making limbs in humans and, essentially, all other legged vertebrates. In snakes, it's broken," says Axel Visel, a geneticist at the Lawrence Berkeley National Laboratory and senior author on the paper. "It's probably one of several evolutionary steps that occurred in snakes, which, unlike most mammals and reptiles, can no longer form limbs."

Today's serpents have undergone one of the most dramatic body plan changes in the evolution of vertebrates. To study the molecular roots of this adaptation, Visel and his colleagues started looking at published snake genomes, including the genomes from basal snakes such as boa and python, which have vestigial legs -- tiny leg bones buried in their muscles -- and advanced snakes, such as viper and cobra, which that have lost all limb structures. Within these genomes, they focused specifically on a gene called Sonic hedgehog, or Shh, involved in many developmental processes -- including limb formation. The researchers delved further into one of the Shh gene regulators, a stretch of DNA called ZRS (the Zone of Polarizing Activity Regulatory Sequence) that was present but had diverged in snakes.

To determine the consequences of these mutations, the researchers used CRISPR, a genome-editing method, to insert the ZRS from various other vertebrates into mice, replacing the mouse regulator. With the ZRS of other mammals, such as humans, the mice developed normal limbs. Even when they inserted the ZRS from fish, whose fins are structurally very different from limbs, the mice developed normal limbs. However, when the researchers replaced the mouse ZRS with the python or cobra version, the mice went on to develop severely truncated forelimbs and hindlimbs.

"Using these new genomic tools, we can begin to explore how different evolutionary versions of the same enhancer affect limb development and actually see what happens," says Visel. "We used to be mostly staring at sequences and speculating about molecular evolution, but now, we can really take these studies to the next level."

To identify the mutations in the snakes' ZRS that were responsible for its inactivation during snake evolution, the researchers took a closer look at the evolutionary history of individual sequence changes. By comparing the genomes of snakes and other vertebrates, they identified one particularly suspicious 17 base-pair deletion that only occurred in snakes; this deletion removed a stretch of the ZRS that has a key role in regulating the Shh gene in legged animals.

The research team turned back the evolutionary clock, restoring the missing 17 base pairs in an artificially created hybrid version of the python ZRS, and tested the edited DNA in mice. Those that carried this evolutionarily "resurrected" ZRS in their genome, replacing their normal regulator, developed normal legs. However, Visel cautions that the evolutionary events were probably more complex than just the one deletion: "There's likely some redundancy built into in the mouse ZRS. A few of the other mutations in the snake ZRS probably also played a role in its loss of function during evolution."

Primitive people (stock image). New research results suggest that
throughout Eurasia, ancient populations interbred less than previously
believed, and that -- contrary to previous findings -- the level of
mixing with Neanderthals did not differ significantly between Europe and
East Asia.

Relationships between the ancestors of modern humans and other archaic populations such as Neanderthals and Denisovans were likely more complex than previously thought, involving interbreeding within and outside Africa, according to a new estimator developed by geneticists. Findings were reported at the American Society of Human Genetics (ASHG) 2016 Annual Meeting in Vancouver, B.C.

In recent years, genetics has led to the revision of many assumptions about archaic populations, explained Ryan J. Bohlender, PhD, a postdoctoral researcher at the University of Texas MD Anderson Cancer Center and first author on the research. For example, the 2010 release of the Neanderthal genome led to the discovery that Neanderthals and the ancestors of modern Europeans interbred. A few years later, scientists discovered the existence of Denisovans, a population known of only through genetics, through a fossilized sample of DNA.

"My colleagues and I set out to find out what we might share with these ancient populations and how our histories interacted," Dr. Bohlender said. They developed an estimation tool to model these interactions based on parameters such as current estimates of population size and dates when populations separated -- how long ago they stopped interbreeding -- and look for inconsistencies with information known from genetic studies about the overlap between the modern human genome and those of ancient populations. Compared to previous estimators, this one made increased use of genetic data to cut down on statistical bias. The researchers then allowed estimates of population size and separation dates to vary in a series of simulations, in order to find out if adjusting these parameters better fit the genetic data.

"Using this process, we found that the population in Africa was likely about 50 percent larger than previously thought. We also found that an archaic-modern human separation date of 440,000 years ago was the best fit, suggesting that Neanderthals diverged from our lineage 100,000 years more recently than we thought," Dr. Bohlender said. "We got the same separation date using data from multiple modern human populations, which is a good sign."

In addition, their results suggest that throughout Eurasia, ancient populations interbred less than previously believed, and that -- contrary to previous findings -- the level of mixing with Neanderthals did not differ significantly between Europe and East Asia.

The findings bring up many new questions, including to what extent the new estimator can be trusted, why it produces results that differ from prevailing estimates, and how to reconcile these differences.

"Overall, our findings confirm the human family tree is more complicated than we think it is," Dr. Bohlender said. "For example, other archaic populations are likely to have existed, like the Denisovans, who we didn't know about except through genetics." They plan to try out simulations with multiple other populations, to see if this adds some clarity to the results.

Dr. Bohlender also believes that more detailed studies of African populations may shed some light. "Africans have been underrepresented in genetics research -- they're not as well studied as European and Asian populations, yet they are more diverse genetically than any other group," he said.